Field of the Invention
The present invention relates to data storage on a disk drive and how to organize files on the disk drive.
Background of the Related Art
A hard disk drive is a data storage device including one or more rotating disks coated with magnetic material. An actuator arm is controllable moved to position a read/write head in alignment with a desired track as the disk rotates under the read/write head. The amount of time required to access data on the hard disk drive (“access time”) is affected by the amount of time required to move the read/write head to the desired track (“seek time”), the amount of time required for the desired disk sector to rotate under the already positioned read/write head (“rotational latency”), and the rate at which data can be transferred from the disk and a disk buffer to an attached computer (“data transfer rate”). The seek time is generally determined by the design of a voice coil designed to rotate an arm that supports the read/write head just above the surface of the disk. The rotational latency is generally determined by the rotational speed of the disk, which is often express in rotations-per-minute (RPM), such that a higher rotational speed results in a lower rotational latency.
Disk fragmentation can occur when the free space on a disk prevents a file from being written in a contiguous area of the disk. Accordingly, smaller portions (fragments) of the file are stored in separate areas. Therefore, accessing a file with two fragments requires repositioning of the read/write head two times, once for each fragment. The increase in movement of the read/write head can have a large impact on system performance. Over a long period of use, disk fragmentation tends to get worse and system performance will continue to suffer.
Fortunately, it is possible to reduce the amount of fragmentation on a disk using a process called defragmentation. Defragmentation programs generally attempt to organize files into fewer fragments and create large unused areas that can be used for contiguous storage of new files. While a defragmentation program or process may be manually initiated by a user, such a process may also be scheduled for off-peak hours to keep disk fragmentation from significantly reducing system performance.